The invention relates to a hob with cutting plates for making gears.
A hob is known (DE-OS No. 2 700 525), wherein the known cutting plates, which consist of hard metal, are distributed helix-like on disk-like gear rims which are provided with plane parallel front faces. Thereby, it is possible that the plate seats can be made by means of milling, so that the total tool does not have to be replaced when individual plate seats wear out, but that only individual parts have to be replaced. However, a disadvantage of the known device is that no diplacement of the individual teeth with respect to each other is possible, due to the even design of the disk-like gear rim. However, a twist like displacement of the teeth is advantageous, because a more favorable cutting ratio is obtained during the operation of the hob and also cuts more evenly if not a few or a plurality of teeth are engaged, but rather sequentially, whereby a time delay is obtained caused by the dimension of the displacement or the dimension of the twist angle .gamma.. Basically, it is possible to provide a displacement for the sequentially engaging teeth when using disk like tooth rims which are provided with reversible cutting plates on their teeth. However, a prerequisite would be that the individual disks are not even, so that the manufacturing costs for such a hob and also the storage costs for the replacement parts would be considerably increased. In addition, the life span of the plate seats for receiving the cutting plates are different, because the tooth stresses within the engagement area are different, in particular during the rough hob milling into the full material. This can be taken into consideration in the known device by exchanging a complete disk like gear rim with another. However, this requires that the hob must be dismantled from the hob machine and must be dismantled into its individual components.
In addition, these known milling devices are only single threaded.